From 13536ddd8c872685baba158a42a7b2ad37129b37 Mon Sep 17 00:00:00 2001
From: Alex Boten <223565+codeboten@users.noreply.github.com>
Date: Thu, 17 Oct 2024 06:03:50 -0700
Subject: [PATCH] config: fix bug where WithResourceAsConstantLabels wasn't set
 (#6260)

There was a bug in the config package where the
WithResourceAsConstantLabels option wasn't appended to the list of
options for the Prometheus reader. Fixed that issue and added a test to
validate the correct number of options is set.

---------

Signed-off-by: Alex Boten <223565+codeboten@users.noreply.github.com>
---
 CHANGELOG.md          |  1 +
 config/metric.go      | 42 ++++++++++++++++++++++++++----------------
 config/metric_test.go | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+), 16 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 93bb4251ccc..d641da679c5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Transform nil attribute values to `log.Value` zero value instead of panicking in `go.opentelemetry.io/contrib/bridges/otelzap`. (#6237)
 - Transform nil attribute values to `log.Value` zero value instead of `log.StringValue("<nil>")` in `go.opentelemetry.io/contrib/bridges/otelslog`. (#6246)
 - Fix `NewClientHandler` so that `rpc.client.request.*` metrics measure requests instead of responses and `rpc.client.responses.*` metrics measure responses instead of requests in `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc`. (#6250)
+- Fix issue in `go.opentelemetry.io/contrib/config` causing `otelprom.WithResourceAsConstantLabels` configuration to not be respected. (#6260)
 
 <!-- Released section -->
 <!-- Don't change this section unless doing release -->
diff --git a/config/metric.go b/config/metric.go
index 743d594456e..fb2dd23905c 100644
--- a/config/metric.go
+++ b/config/metric.go
@@ -298,28 +298,16 @@ func newIncludeExcludeFilter(lists *IncludeExclude) (attribute.Filter, error) {
 }
 
 func prometheusReader(ctx context.Context, prometheusConfig *Prometheus) (sdkmetric.Reader, error) {
-	var opts []otelprom.Option
 	if prometheusConfig.Host == nil {
 		return nil, fmt.Errorf("host must be specified")
 	}
 	if prometheusConfig.Port == nil {
 		return nil, fmt.Errorf("port must be specified")
 	}
-	if prometheusConfig.WithoutScopeInfo != nil && *prometheusConfig.WithoutScopeInfo {
-		opts = append(opts, otelprom.WithoutScopeInfo())
-	}
-	if prometheusConfig.WithoutTypeSuffix != nil && *prometheusConfig.WithoutTypeSuffix {
-		opts = append(opts, otelprom.WithoutCounterSuffixes())
-	}
-	if prometheusConfig.WithoutUnits != nil && *prometheusConfig.WithoutUnits {
-		opts = append(opts, otelprom.WithoutUnits())
-	}
-	if prometheusConfig.WithResourceConstantLabels != nil {
-		f, err := newIncludeExcludeFilter(prometheusConfig.WithResourceConstantLabels)
-		if err != nil {
-			return nil, err
-		}
-		otelprom.WithResourceAsConstantLabels(f)
+
+	opts, err := prometheusReaderOpts(prometheusConfig)
+	if err != nil {
+		return nil, err
 	}
 
 	reg := prometheus.NewRegistry()
@@ -358,6 +346,28 @@ func prometheusReader(ctx context.Context, prometheusConfig *Prometheus) (sdkmet
 	return readerWithServer{reader, &server}, nil
 }
 
+func prometheusReaderOpts(prometheusConfig *Prometheus) ([]otelprom.Option, error) {
+	var opts []otelprom.Option
+	if prometheusConfig.WithoutScopeInfo != nil && *prometheusConfig.WithoutScopeInfo {
+		opts = append(opts, otelprom.WithoutScopeInfo())
+	}
+	if prometheusConfig.WithoutTypeSuffix != nil && *prometheusConfig.WithoutTypeSuffix {
+		opts = append(opts, otelprom.WithoutCounterSuffixes())
+	}
+	if prometheusConfig.WithoutUnits != nil && *prometheusConfig.WithoutUnits {
+		opts = append(opts, otelprom.WithoutUnits())
+	}
+	if prometheusConfig.WithResourceConstantLabels != nil {
+		f, err := newIncludeExcludeFilter(prometheusConfig.WithResourceConstantLabels)
+		if err != nil {
+			return nil, err
+		}
+		opts = append(opts, otelprom.WithResourceAsConstantLabels(f))
+	}
+
+	return opts, nil
+}
+
 type readerWithServer struct {
 	sdkmetric.Reader
 	server *http.Server
diff --git a/config/metric_test.go b/config/metric_test.go
index 8d7ced508ca..3940e765b20 100644
--- a/config/metric_test.go
+++ b/config/metric_test.go
@@ -1138,3 +1138,44 @@ func TestNewIncludeExcludeFilterError(t *testing.T) {
 	}))
 	require.Equal(t, fmt.Errorf("attribute cannot be in both include and exclude list: foo"), err)
 }
+
+func TestPrometheusReaderOpts(t *testing.T) {
+	testCases := []struct {
+		name        string
+		cfg         Prometheus
+		wantOptions int
+	}{
+		{
+			name:        "no options",
+			cfg:         Prometheus{},
+			wantOptions: 0,
+		},
+		{
+			name: "all set",
+			cfg: Prometheus{
+				WithoutScopeInfo:           ptr(true),
+				WithoutTypeSuffix:          ptr(true),
+				WithoutUnits:               ptr(true),
+				WithResourceConstantLabels: &IncludeExclude{},
+			},
+			wantOptions: 4,
+		},
+		{
+			name: "all set false",
+			cfg: Prometheus{
+				WithoutScopeInfo:           ptr(false),
+				WithoutTypeSuffix:          ptr(false),
+				WithoutUnits:               ptr(false),
+				WithResourceConstantLabels: &IncludeExclude{},
+			},
+			wantOptions: 1,
+		},
+	}
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			opts, err := prometheusReaderOpts(&tt.cfg)
+			require.NoError(t, err)
+			require.Len(t, opts, tt.wantOptions)
+		})
+	}
+}